Production of viscose rayon



United States Patent 3,153,687 PRODUCTION OF VISCOSE RAYON BrewsterBlanton Eskridge, Candler, N.C., assignor to American Enka Corporation,Erika, N.C., a corporation of Delaware No Drawing. Filed Jan. 17, 1962,Ser. No. 166,908 4 Claims. (Cl. 264-191) This invention relatesgenerally to the manufacture of rayon threads, fibers, yarn and the likeproducts hereinafter referred to collectively as yarn and moreparticularly to the production of high modulus viscose rayon yarncharacterized by its high strength and low elongation values making itespecially suitable for use in rug backing and in reinforcing rubberproducts such as belting and the like.

Yarn having high strength and low elongation values is commonly referredto as high modulus yarn. The modulus of yarn is determined by thefollowing formula:

wherein M is modulus, S is break strength in grams per denier, and E ispercent of elongation. Accordingly, in order for yarn to have a highmodulus, it must have a high breaking strength and an attendant lowpercentage of elongation.

In an effort to obtain high modulus rayon yarn, numerous modificationsin rayon manufacturing processes have been proposed wherein variouscombinations of modifiers and other additives are employed atmiscellaneous stages during the production of the yarn.

A process of particular significance is that disclosed in applicationSerial No. 740,189, having common ownership herewith, wherein a viscosecontaining an ethoxylated amine modifier is extruded into an acidspinning bath. The threads thus-produced are then aftertreated bypassing them through a cold intermediate bath con taining formaldehyde,and then through a hot stretch bath. In another process, disclosed inUS. Patent N01 3,007,766, a viscose containing an alkali metal salt andmodifiers, such as polyethylene glycol, ethoxylated amines and theirquaternized derivatives is extruded into an acid spinning bath followedby passing the thus-produced threads through an intermediate bathcontaining formaldehyde and then through a hot acid stretch bath alsocontaining formaldehyde.

While the use of formaldehyde in an intermediate and third bath impartsimproved properties to the threads, in that they possess a higher modulithan that obtainable solely with the use of modifiers in combinationwith a cold intermediate bath, there are nevertheless certaindisadvantages to its use in this manner. The cost of installing andmaintaining an intermediate bath is a major factor in the expense ofsuch a high modulus system. Furthermore, formaldehyde vapors escapingfrom the baths create extremely unsatisfactory operating conditions forworkers employed in plants using this system due to objectional odorsand disagreeable effects thereby produced. Moreover, consumption offormaldehyde is high, which increases the operating costs of thissystem.

' Accordingly, it is an object of this invention to provide a processfor manufacturing high modulus viscose rayon yarn not having thedisadvantages inherent in the known processes.

An additional object of this invention is to provide a simple andeconomical process for producing high modulus viscose rayon yarn.

Another object is to provide a process for producing high modulusviscose rayon yarn having high strength and low elongation values.

A still further object of this invention is. to provide a process forproducing viscose rayon yarn utilizing a novel combination of modifierswhereby a viscose rayon yarn with improved physical properties isproduced;

These and other objects will become apparent from the following detaileddescription.

It has been discovered that the above objects may be accomplished byintroducing small amounts of a lower aliphatic aldehyde into the viscoseunder certain critical conditions, thereby eliminating the aldehydecontaining intermediate bath and the disadvantages and expense incidentthereto. In accordance with this invention, high modulus viscose rayonyarn having a high breaking strength and low elongation is obtained whena small amount of formaldehyde is introduced into the viscose inaddition to other known modifiers. The addition of the formaldehydeshould be carried out in an indirect manner by adding it to the causticsoda solution (dissolving lye) for the cellulose xanthate crumbs. Thisshould be done immediately prior to the addition of the crumbs to thesolution, thereby assuring uniform dispersion throughout the resultingviscose solution. It is very critical that the formaldehyde bethoroughly mixed with viscose and that it be added to the viscoseindirectly through the dissolving lye. Adding it to the viscose at anysubsequent stage of CiV).

modulus yarn as when it is added to the dissolving lye. The amount offormaldehyde used may vary within a range of from 0.05% to 1.0%, basedon oven dry recoverable cellulose in viscose (hereinafter abbreviated asThe preferred amount of formaldehyde is 0.5% CiV. While amounts higherthan 1.0% CiV may be used, such increased amounts result in no furtherimprovement in the yarn.

The formaldehye is used in combination with other so-called modifiers inthe viscose such as the polyglycols, alkoxylated amines, and theirquaternary derivatives. The alkoxylated amines are known in the art asEthomeens and are described in detail in US. Patent No. 2,978,292, thedisclosure of which is incorporated herein by reference. Theirquaternary derivatives are known as Ethoquads and are described indetail in application Serial No. 609,792, filed September 14, 1956,having common ownership herewith. The polyglycol used is preferablyeither polyethylene glycol or polypropylene glycol, the molecular weightof which may vary depending upon the spinning conditions and theparticular amine employed. These modifiers may be present to the extentof 0.3% to 5.0% CiV.

In the preparation of viscose according to this invention, the source ofthe cellulose may be wood pulp, cotton linters, or a mixture thereof.The cellulose content of the viscose may range from about 5.0%-8.5%. Theamount of carbon disulfide used during the xanthation *Registeredtrademarks of Armour and Company.

step may vary from 25-60% CiV, with the preferred amount being 38%-40%.In general, the viscose is aged to approximately the same level ofmaturity before spinning as that normally used. For example, a 7.3-5.5(percent cellulose-percent total alkali) viscose may have a Hottenrothmaturity index varying at spinning from about 8-20. However, it ispreferred to keep the maturity in the 13-145 range for best spinnabilityand properties.

In order to determine proper maturity control, a comparison was madebetween viscose solutions containing formaldehyde and viscose solutionswith no formaldehyde. As is readily apparent from the representativeexamples set forth in the table below, the addition of formaldehyde tothe dissolving lye accelerate the second aging consider The effect offormaldehyde on the xanthate ratio as plotted against the maturity indexcan be seen in the following graph wherein a viscose solution containing0.5% formaldehyde is compared with a viscose solution containing noformaldehyde.

X ANTHATE RAT/O -t= 01 F f HoTTE/vRoTH MATURIT) INDEX I C! Nun 135R)Viscose prepared in accordance with this invention is extruded into anacid primary bath, from which the filaments thus-produced are withdrawnand highly stretched, preferably in a hot acidic secondary bath. Theyare then aftertreated in the usual manner. The primary spinbath containsan aqueous solution of from 2%-10% sulfuric acid, 3%-26% sodium sulfateand 1%-9% zinc sulfate. For special purposes, other metal salts may besubstituted for the zinc sulfate. Preferably the total salt contentshould not exceed 15%. In addition, modifiers such as the alkoxylatedamines may be present in small quantities. Stretching is preferablycarried out in a dilute sulfuric acid containing second bath, maintainedat a temperature of about 80100 C. Small quantities of sodium and Zincsulfates may also be present in this bath. The spinning stretch ispreferably adjusted to 1 gram per denier.

The invention will be more clearly understood by reference to theexamples and discussions which follow. These examples are given forillustrative purposes only and are not to be construed as limitative.All concentrations used herein unless otherwise designated arecalculated as percentages by weight based on the viscose solution or thespinbaths.

Example I Alkali cellulose was prepared in the conventional manner fromwood pulp and aged to obtain a degree of polymerization that would yielda viscose solution viscosity of 50-60 seconds by the ball fall method.The alkali celluose was xanthated with carbon disulfide and the xanthatethus obtained was dissolved in a caustic soda solution containing (1)0.05% CiV formaldehyde added immediately prior to dissolving; (2) 1.5%CiV of an ethoxylated coconut oil amine (available commercially asEthomeen C-25 from Armour and Company) having the general formula inwhich n is 12 to 14 and x+y=about 15; and (3) 1.5 CiV polyethyleneglycol having a molecular weight of at least 2000. After dissolving, aviscose was obtained having a composition of 7.3% cellulose, 5.5% sodiumhydroxide and 2.25% total sulfur. The freshly prepared viscose solutionwas deaerated, filtered, and ripened to a Hottenroth maturity index ofabout 13.5.

The viscose solution was extruded into a primary spinbath containing5.0% H 8.5% Na SO 5.0% ZnSO plus 1000-2000 parts per million of EthomeenC-25. The temperature of the spinbath was maintained at 42 C. After atravel of 24 inches through the spinbath, the yarn was withdrawn andpassed through a secondary bath containing 3.0% H 80 1.4% Na SO and 0.5%ZnSO maintained at a temperature of 92 C. for an immersion distance of40 inches. The yarn thus produced was then collected in a rotating pot.A tension of 1600 grams was maintained in the secondary bath to producea stretch of The collected yarn was aftertrealted in the conventionalmanner and tested for strength and elongation in both conditioned andwet state. The properties of the yarn are set forth in Table II.

Five 73/ 5.5/ 2.3 (percent cellulose-percent total alkalipercent totalsulfur) viscoses were prepared in a manner similar to that described inExample I. One was a contnol and contained no formaldehyde. The otherfour contained varying amounts of modifiers. All were aged to aHottenroth maturity index of 16-20. Samples of each were extruded intospinbaths containing different percentages of H 80 The other additivesto the spinbath were held constant at 8.5% Na SO and 5.0% ZnSO Theprimary spinbaths were maintained at a temperature of 42 C. with theimmersion distance being 28 inches. The secondary baths all contained2.4% H 50 1.1% Na SO and 0.5 ZnSO and were maintained at 92 C. Tensionwas adjusted to 1100 grams per denier. All yarn samples contained 1100filaments and averaged approximately 1100 denier.

TABLE III Control, 1.5% 1 0.5% 1 01110, 1.5% 1 0.5% CH O, 0.5% 1 0.5% 1(EH 0, 3.0% 1 1.0% CH O, 1.5% 1 Ethorneen C-25, 1.5% 1 Ethomeen O-25,1.5% 1 Ethomeen (J-25, 3.0% 1 Polyethylene Ethomeen C25, 1.5% 1Polyethylene Glycol Polyethylene Glycol Polyethylene Glycol GlycolPolyethylene Glycol Percent Cond. Cond Cond Cond. Cond. nd Cond. Cond.Cond. Oond.

H2804 Stgth, Elon, Mod. Stgth, Elon., Mod. Stgth, Elon., Mod. Stgth.,Elon., Mod. Stgth El0n., Mod. added to g./d. Percent gJd. Percen g./d.Percen g./d. Percent g./d. Percent spinbath 1 All percentages based oncellulose in viscose.

Example III Five 73/55/225 (percent cellulose-percent totalalkali-percent total sulfur) viscoses were prepared using the sameprocedure as that described in Example I. All were aged to a Hottenrothmaturity index of 1314.5. Viscosity was 5060 seconds, ball fall method.Diifen ent percentages of formaldehyde were used in each sample, theremaining additives being constant at 0.5% CiV polyethylene glycol and2.0% CiV Ethomeen C-25. Each viscose was extruded into a spinbathcontaining 5.0% H 80 8.5% Na SO and 5.0% ZnSO plus 1000-2000 parts permillion Ethorneen C-25. Temperature of the spinbath was maintained at 42C., with immersion for 24 inches. The secondary bath composition was3.0% H SO 1.4% Na SO and 0.5% ZnSO With the temperature being 93 C.Immersion distance was 40 inches. Tension and stretch were the same asin Example I. The

results were as follows:

TABLE IV Percent CiV Formaldehyde in Viscose Conditioned Strength, g/d4. 81 5. 27 5. 24 5. 16 5. 24 5. 51 Conditioned Elongation, Percent 14.8 14. 9 l5. 2 15.6 15.6 15.5 Modulus (cond.) 32. 5 35.4 34. 5 33.1 33. 635. 5 Wet strength, g/d 3. 68 3. 72 3.68 3. 40 3.69 Wet elongation,Percent 17. 8 18. 1 18. 4 17.7 18. 1 Modulus (wet) 20. 7 20. 6 20. 0 19.2 20. 4

As the foreoing examples clearly show, a high strength low elongationand high modulus yarn can be prepared in accordance with this inventionby incorporating formaldehyde in the viscose. Such procedure eliminatesthe use of an expensive intermediate bath system. Most important,however, escaping formaldehyde fumes, necessarily present with theintermediate bath system are likewise eliminated.

While preferred embodiments of the invention have been shown, it is tobe understood that changes and variations may be made herein withoutdeparting from the spirit and scope of the invention as defined by thefollowing claims.

What is claimed is:

1. A process for the production of high strength, low

elongation viscose rayon yarn and like products which comprisesextruding a viscose solution containing from 0.05% to 0.5 formaldehyde,based on the cellulose in viscose, prepared by adding the formaldehydeto the dissolving lye for the cellulose xanthate, and from 0.3% to 5.0%of a modifier based on the cellulose in the viscose, said modifierselected from the group consisting of polyglycols, alkoxylated amines,and their quaternized derivatives, into an acid coagulating andregenerating bath, and collecting the yarn.

2. In the viscose process the improvement comprising dissolving thecellulose xanthate crumbs in a caustic soda solution containing from0.05% to 1.0% formaldehyde based on the cellulose in viscose and from0.3% to 5.0% of a modifier based on the cellulose in viscose, saidmodifier selected from the group consisting of polyglycols, alkoxylatedamines, and their quaternized derivatives, spinning the viscose into anacid coagulating and regenerating bath and stretching the resultantfilaments whereby a high strength, low elongation filamentary product isobtained.

3. In the viscose process the improvement comprising dissolving thecellulose xanthate crumbs in a caustic soda solution containing from0.05% to 1.0% formaldehyde based on the cellulose in viscose,incorporating from 0.3% to 5.0% of a modifier based on the cellulose inviscose in the resultant viscose solution prior to spinning, andmodifier selected from the group consisting of polyglycols, allcoxylatedamines, and their quaternized derivatives, spinning the viscose into anacid coagulating and regenerating bath, and stretching the resultantfilaments whereby a high strength, low elongation filamentary product isobtained.

4. A process for producing high strength, low elongation rayon productscomprising dissolving cellulose Xanthate crumbs in a caustic sodasolution containing from 0.05% to 1% formaldehyde based on the cellulosein viscose and from 0.3% to 5% of a modifier based on the cellulose inviscose, said modifier selected from the group consisting ofpolyglycols, alkoxylated amines, and their quaternized derivatives,aging the resultant viscose solution, spinning the aged viscose into anacid and coagulating and regenerating bath and thereafter stretching thethus produced product.

Ubbelohde June 29, 1943 Mitchell et a1. Jan. 23, 1962

1. A PROCESS FOR THE PRODUCTION OF HIGH STRENGTH, LOW ELONGATION VISCOSERAYON YARN AND LIKE PRODUCTS WHICH COMPRISES EXTRUDING A VISCOSESOLUTION CONTAINING FROM 0.05% TO 0.5% FORMALDEHYDE, BASED ON THECELLULOSE IN VISCOSE, PREPARED BY ADDING THE FORMALDEHYDE TO THEDISSOLVING LYE FOR THE CELLULOSE XANTHATE, AND FROM 0.3% TO 5.0% OF AMODIFIER BASED ON THE CELLULOSE IN THE VISCOSE, SAID MODIFIER SELECTEDFROM THE GROUP CONSISTING OF POLYGLYCOLS, ALKOXYLATED AMINES, AND THEIRQUATERNIZED DERIVATIVES, INTO AN ACID COAGULATING AND REGENERATING BATH,AND COLLECTING THE YARN.